If you have an AT&T iPhone, do you know what it is doing in the wee hours of the morning? According to Gear Diary’s Douglas Moran, AT&T iPhone’s phone home about 150MB (that’s megabytes) every night.
This 150MB per night is not supposed to be counted against an account’s 3G data quota. However, it was in his daughter’s case and caused data overage problems. So, if your data use seems a lot higher than you think it should be, you might wan to carefully monitor data use as Douglas Moran did. However, note the one incorrect assumption he made: He though that turning off 3G would shut off data transfers. This is not the case. Shutting off 3G forces using the slower EDGE network. So, data is still going through AT&T’s network. It is simply being transferred very slowly.
The real question is: What in the world is AT&T doing with the 150MB data it reportedly transfers from your iPhone each night? And, what if you have your iPhone in flight mode (all radios turned off) at night? Does this 150MB get transferred during the day? Perhaps this is why AT&T’s network can’t deal efficiently with iPhone data traffic.